new data regarding the lens of the eye · new data regarding the lens of the eye (for radiation...

NEW DATA REGARDING

THE LENS OF THE EYE

(FOR RADIATION PROTECTION PURPOSES)

EU Scientific Seminar, Emerging issues with regard to organ doses

Luxembourg, 17th May 2017, Bordy Jean-Marc

! !

EU Scientific Seminar, Emerging issues with regard to organ doses | Bordy Jean-Marc | 2

LNE

French National Metrological Institute

LNE / CEA / LNHB

French National metrological laboratory for Ionizing radiations

It develops and transfers to the end users references in terms of air kerma,

absorbed doses and dose equivalents for radiotherapy, radio diagnosis and

radiation protection (public, patients, workers).

Institut CEA LIST

Commissariat à l’énergie atomique et aux énergies alternative

CEA Saclay / PC 111 / F-91191 Gif sur Yvette CEDEX

Tel. +33 (0)1 69 08 41 89 / [email protected]

INTRODUCTION


INTRODUCTION

The lens of the eye is a special case:

First, it is included in the ICRP’s list of organs to calculate the effective dose - E

Second, one can do routine individual monitoring of eye lens equivalent dose -

Hlens - thoughout the operational quantity (dose equivalent Hp(3))

Today, we will speak about RADIATION PROTECTION for eye lens dosimetry

Part of this work was already presented or published in:

Radioprotection 50(3), 177-185 (2015) | Monitoring of eye lens doses in radiation protection / Bordy JM

DOI:10.1051/radiopro/2015009

Technical information sheets of the Société Française de RadioProtection SFRP: Eye lens – Regulatory

limits, Measurement, Dosimetry and Medical surveillance.

http://www.sfrp.asso.fr/medias/sfrp/documents/Divers/Fiche_SFRP_-_Eye_Lens_-_GB___06-2016_V2.pdf

Individual monitoring IM2015 / Bruges – Belgium and EPRI 2016 / Charlotte - North Carolina - USA |

Proposal for a criterion to choose between a direct or indirect evaluation of eye lens doses / Bordy JM

Other references on the definition of the dose equivalent quantity are given on slide 8 of this presentation

http://www.sfrp.asso.fr/medias/sfrp/documents/Divers/Fiche_SFRP_-_Eye_Lens_-_GB___06-2016_V2.pdf

Conv. Coef.

…/…

kerma

Dose Equivalents

Hp(3), Hp(10), …

Effective dose, E

Equivalent Doses, Hlens …

Estimate

Protection quantities

Sv/Gy

Operationnal quantities

Sv

Simplified phantoms

Sphere

Chest, finger, wrist

Calibration

Dosimeters

GENERAL SCHEME FOR RAD. PROT. QUANTITIES


Hp(3) ~ Hlens

“Primary”

dosemeters

Primary Quantities

Gy

What we need to know – Hlens

What we have to measure – Hp(3)

LNE CEA LNHB

TO BE ABLE TO MONITOR IR EXPOSURES

Operationnal Quantities (OQ) Hp(d) - H’(d) or H*(10)(tissu equivalent phantoms)

Dosimeter satisfying type test requirements

Calibration in terms of OQ (on phantom / free in air)

Dosimeter used/worn as specified

In international recommandations

Measure/evaluation of operationnal quantities at workplaces

Estimate of Hskin, Hlens, E

Check the exposure limits

indiv. Area


Operationnal Quantities (OQ) Hp(3) - H’(3)(tissu equivalent phantoms)





Measure/evaluation of operationnal quantities at workplace

Estimate of Hlens


indiv. Area

ISO 12794

150 mSv /year

APPLICATION TO EYE LENS DOSIMETRY


0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

1,8

0,01 0,1 1 10

Dcri

st.

Hp(0

,07

) H

'(0

.07

)/

Kair

Energie des photons (MeV)

Dcristallin / Kair ICRP 74

Hp(0,07,0°) / Kair

H'(0,07,0°) / Kair

~1,08

Hp(0,07) et H’(0,07) quite similar to DLens

~1,1

Except below ~20 keV

COMPARAISON WITH DLENS

NORMAL INCIDENCE

Dlens / kair

Dle

ns

Photon energy

E would « cover » Hlens

because of the limit at 150 mSv








Estimate of Hlens


indiv. Area

Hskin ; E Conservatives

ISO 12794

150 mSv /year









Estimate of Hlens


indiv. Area

Hskin ; E Conservatives

ISO 12794

150 mSv /year

???

20 mSv /year



CEA LNE LNHB – ENEA works on the definition of Hp(3) – ORAMED project

- Definition of the quantity Hp(3) clarified through the use of cylinder

(H=D=20cm) made of ICRU tissue as the phantom

- Use of a water cylindrical phantom with PMMA walls (H=D=20cm) for

calibration purposes (ISO 29661 & future revised version of ISO DIS 4037)

Principle for the design of radiation protection dosemeters for operational and protection quantities, J.M. Bordy, G.

Gualdrini, J. Daures and F. Mariotti, Radiation protection dosimetry, (2011) 144(1-4): 257-261

Monte carlo determination of the conversion coefficients Hp(3)/Ka in a right cylinder phantom with penelope code.

comparison with "mcnp" simulations“ J. Daures, J. Gouriou, J.M. Bordy,

Radiation Protection Dosimetry (2011) 144(1-4): 37-42 ; more details in Conversion coefficients from air kerma to

personal dose equivalent, Hp(3) for eye-lens dosimetry, Daures, J., Gouriou, J. and Bordy, J.-M., ISSN/0429-3460,

CEA-R-6235. CEA (2009)

Eye lens dosimetry: task 2 within the ORAMED project G. Gualdrini, F. Mariotti, S. Wach, P. Bilski, M. Denoziere,

J. Daures, J.M. Bordy, P. Ferrari, F. Monteventi, and E. Fantuzzi; Radiation Protection Dosimetry (2011) 144(1-4):

473-477

ORAMED project. Eyelens dosimetry. A new Monte Carlo approach to define the operational quantity Hp(3).,

Marriotti, F. and Gualdrini, G., ISSN/0393-3016, RT/2009/1/BAS. ENEA (2009)

Dose conversion coefficients for photon exposure of the human eye lens, Behrens, R. and Dietze, G., 2011 Phys.

Med. Biol. 56 415–437. …/…

WE NEED Hp(3)


Hp(3,0°) better than Hp(0,07, 0°) et H’(0,07)

COMPARAISON WITH DLENS

NORMAL INCIDENCE


A few individual dosemeters are commercially available (list not exhaustive)

the principle is to allow a morphological adaptation as ergonomic as possible

WE NEED DOSIMETERS FOR A DIRECT MEASUREMENT OF HP(3)

www.radpro-int.com / assets / eye-d.pdf

RadCard : EYE-D ™.

UK rotundascitech company*

http: // www.rotundascitech.com/EyeDosimetry.html

DOSIRIS

IRSN

http://dosimetre.irsn.fr/fr-

fr/Documents/Fiches%20produits/IR

SN_Fiche_dosimetre_Cristallin.pdf

Landauer

http://www.landauer-fr.com/lentreprise/actualites.html

* Health Protection Agency (HPA) proposed a similar design

dosilab – dosiEYEhttp://www.dosilab.fr/


http://dosimetre.irsn.fr/fr-fr/Documents/Fiches produits/IRSN_Fiche_dosimetre_Cristallin.pdf

http://www.dosilab.fr/

Operationnal Quantities (OQ) Hp(3) cylinder 20cm « head » (tissu equivalent phantom)

Dosimeter satisfying type test requirements (IEC 62387)

Calibration in terms of OQ (on head phantom)


In international recommandations (ISO 15382)

Measure/evaluation of operationnal quantities in laboratories

Estimate of Hlens

Verification of the exposure limits

indiv.

PRESENT SITUATION OF EYE LENS DOSIMETRY


20 mSv /year

50 mSv/year

Even if it is agreed that lens “doses” must be measured/monitored, the

modalities of its implementation is the cause for debate.

Of course, estimate Hlens means a direct measurement of Hp(3) with a

dosimeter specifically designed to measure Hp(3), worn at the level of the

eye, behind individual protections if any (glasses, faceguards)

A compromise solution between the constraint to wear an additional

dosimeter close to the eye, and the need to monitor accurately the lens

exposure, could lead an indirect measurement. That is to say:

o To estimate Hp(3) through HP(10) – whole body dosimetry (chest)

R = Hp(3) / Hp(10)

In such a case, an objective index is needed to justify

if it might be possible to evaluate Hp(3) from another quantity.


PRESENT SITUATION OF EYE LENS DOSIMETRY

Hp(3) +

_

Pre

cis

ion

Hlens

Radiation field

Not homogeneous Homogeneous

Variable Constant20 mSv/y

~0 mSv/y

Hp(3)= R x Hp(10))

One has to keep in mind that the calculation infers a loss in terms of accuracy

So that one has to know to which extend the indirect method can be used.

DIRECT OR INDIRECT THAT IS THE QUESTION


???

???

When Hp(3) = R x Hp(10) can be used « without » a risk to exceed Hp(3) limits?

INDIRECT EVALUATION OF HP(3)


Limit

Hp(3)

Hp(3) =

R x Hp(10)

𝑃 = 1

𝑢(𝐻𝑝3) 2𝜋𝑒−

12 𝐻𝑝 3 −𝐻𝑝 3 𝑚

𝑢(𝐻𝑝3)

2∞

𝐿𝑖𝑚𝑖𝑡𝑒 𝐻𝑝(3)

Limit

Hp(3)

Hp(10)

R = Hp(3) / Hp(10)

Hp(10)

Hp(3) =

R x Hp(10)

u(Hp10) R = Hp(3) / Hp(10)

u(R)

Simple direct

proportionality

With

uncertaintyu(Hp3)

Perfect

World

Real

life

One has to keep

in mind that the

calculation infers

a loss in terms of

accuracy

Taking into account the limit of exposure for Hp(3) (20 mSv on average

over 5 years or 50 mSv over one year), one can substitute Hp(3) for

these exposure limits to define a maximum value of Hp(10) such as:

Hp(10)max20 = Hp(3)max / R or Hp(10)max50 = Hp(3)max / R

For example, if the R = 5, it means that at this workplace, the limit of

exposure in terms of Hp(3) corresponds to a maximum value of Hp(10)

Hp(10)max20 = 4 mSv if Hp(3) limit of 20 mSv

Hp(10)max50 = 10 mSv if Hp(3) limit of 50 mSv

Over these values of Hp(10)max , the limit in terms of Hp(3) is exceeded.

CRITERION TO APPLY AN INDIRECT METHOD

20

20

50

50

/ Hp(10) R = Hp(3) Hp(10) = Hp(3) / R


Perfect World !

Hp(10)max20 = 20 / R or Hp(10)max50 = 50 / R (eq. 1)

When including the uncertainty on Hp(10) measurement

Considering the extended uncertainty U(Hp10) (k=2 or 3 or ..) on the

measurement of Hp(10), equations 1 become:

+ U(Hp10) = / Hp(10)max20 = (20 / R) –

+ U(Hp10) = / Hp(10)max50 = (50 / R) –

Applying these equations and depending on the confidence level, one

can infer that the exposure limit in terms of Hp(3) might not be

exceeded.

If U(Hp10) = 2 mSv and R = 5, Hp(10)max is:

Hp(10)max20 = 2 mSv (4 mSv) if Hp(3) limit 20 mSv

Hp(10)max50 = 8 mSv (10 mSv) if Hp(3) limit 50 mSv


R

20Hp(10)max20

Hp(10)max5050

R U(Hp10)

U(Hp10)


Real

Life !

Hp(10)max20 = (20 / R) – U(Hp10)

Hp(10)max50 = (50 / R) – U(Hp10)

U(Hp10) can be taken from the so called “trumpet curves”

(ISO 14146, 2000, EUR 14852 EN)

0,0

0,5

1,0

1,5

2,0

2,5

0,01 0,1 1 10

Rep

on

se

Hp(10) (mSv)

U(H

p10

)



Equations 2

0,0

0,5

1,0

1,5

2,0

2,5

0,01 0,1 1 10

Rep

on

se

Hp(10) (mSv)

Upper limit is given by

Hp(10)ul = 1.5 Hp(10)t (1 + H0 / (2 H0 + Hp(10)t)) if Hp(10)t≥H0

Hp(10)ul = 2 Hp(10)t if Hp(10)t<H0

Lower limit is given by

Hp(10)ll = Hp(10)t / 1.5 (1 - 2 H0 / (2 H0 + Hp(10)t)) if Hp(10)t≥H0

Hp(10)ll = 0 if Hp(10)t<H0

Where - Hp(10)t is the true value of the dose equivalent.

- H0 is the lowest dose equivalent required to be measured, here

0.17 mSv for Hp(10) for photons for a monthly wearing period

and a limit equal to 20 mSv (EUR 14852 EN), a value of 0.41 mSv

could be used for a limit equal to 50 mSv.

- Hp(10)ul and Hp(10)ll are the upper and lower limits respectively.

It turns that the upper limit is the most penalizing for this use

Upper limit is given by

Hp(10)ul = 1.5 Hp(10)t (1 + H0 / (2 H0 + Hp(10)t)) if Hp(10)t≥H0

Hp(10)ul = 2 Hp(10)t if Hp(10)t<H0



Hp(10)max20 = (20 / R) – U(Hp10) and Hp(10)max50 = (50 / R) – U(Hp10)

Hp(10)ul is taken into account to substitute U(Hp10) for the maximum

error, one has :

if Hp(10) ≥H0

Hp(10)max20= (20 / R) – if Hp(10) <H0

if Hp(10) ≥H0

Hp(10)max50= (50 / R) – if Hp(10) <H0

The last thing to take into account is

the uncertainty, U(R), taken from the evaluation of R

through the workplace study


Hp(10)ul = 1.5 Hp(10) (1 + H0 / (2 H0 + Hp(10))) if Hp(10) ≥H0

Hp(10)ul = 2 Hp(10) if Hp(10) <H0

Hp(10)max20 = (20 / R) –

1.5 Hp(10) (1 + H0 / (2 H0 + Hp(10)))

2 Hp(10)

2 Hp(10)

1.5 Hp(10) (1 + H0 / (2 H0 + Hp(10)))

Hp(10)max50 = (50 / R) –


Introducing the uncertainties, U(R) and U(Hp10) equations 2 become:

Hp(10)max20= (20 / (R+U(R))) – Hp(10) x 1.5 (1 + H0 / (2 H0 + Hp(10)))

if Hp(10) ≥H0

Hp(10)max20= (20 / (R+U(R))) – Hp(10) x 2 if Hp(10) <H0

And

Hp(10)max50= (50 / (R+(U(R))) – Hp(10) x 1.5 (1 + H0 / (2 H0 + Hp(10)))

if Hp(10) ≥H0

Hp(10)max50= (50 / (R+U(R))) – Hp(10) x 2 if Hp(10) <H0

Now we can make a few calculations

based on these equations…



0,1

1

10

100

0,1 1 10 100

Hp(1

0)m

ax

R + U(R)

Limit Hp(3) = 50 mSv Limit Hp(3) = 20 mSv50

20

5

Hp(10)max20 = 2.8 mSv

Hp(10)max50 = 7 mSv



Other trumpet curves equations for Hp(10) (ICRP, IEC) could be introduced in

the model instead of the ISO/EUR ones.


E > 65 keV

E ≤ 65 keV

H0 = 0.1 mSv

H0 = 0.1 mSv



Quite low but visible impact

of the other trumpet curves


http://www.amtsn.asso.fr/IMG/pdf/PrA_c_sentation_EDF_CRISTALLIN.pdf

R = Hp(3) / Hp(10)

Glove box (reprocessing plants)2.78 and 3.34 (photon)

1 (neutron)

Nuclear power plants (PWR) 0,9 to 1,5

Glove box (nuclear medecine) 12.5 (photon)

orthopaedic 10 (X rays)

Interventional radiology 4 (X rays)

Example of ratios, R

Huge variation of R depending on the workplace

So the uncertainty U(R) would be very large

if R covers a large range of workplace situations


EVALUATION OF R AND U(R)

+/- 50%

k=2 ~95%

confidence level


Limit

Hp(3)

Estimated

Value

Hp(3)

u(Hp3)Example for limit Hp(3) = 20 mSv, u(R) = 25%

Probability

lower than

2.7 10-3

IS THE LIMIT EXCEEDED

One can monitor Hlens with direct measurement or indirect evaluation

Conditions to apply the proposed indirect method are:

The Hp(10) dosimeter must fulfill the type test requirements of IEC and

ISO standards (at least within the domain it is used).

The dosimeter is calibrated as recommended in ISO standards.

One must have the results of the workplace study to evaluate R, U(R)

and the expected value of Hp(10) and to check if it is lower than Hp(10)max

to allow using the indirect method.

Taking into account the uncertainty on Hp(10) and R,

we can define the maximum values of Hp(10) below which

the indirect evaluation of Hp(3) is justified

minimizing the risk to « give » an Hp(3) value lower than the limits

while the « real » value of Hp(3) exceed the limit.

CONCLUSIONS


EU Scientific Seminar, Emerging

issues with regard to organ doses

2017 - Luxembourg

CEA LIST

Thank you for

your attention

Monitoring of eye lens doses in radiation protection

Radioprotection 50(3), 177-185 (2015), http://dx.doi.org/10.1051/radiopro/2015009

Technical Information Sheets of SFPR: Eye lens: REGULATORY LIMITS,

MEASUREMENT, DOSIMETRY AND MEDICAL SURVEILLANCE

http://www.sfrp.asso.fr/medias/sfrp/documents/Divers/Fiche_SFRP_-

_Cristallin_VA___01-2016.pdf

Limit

Hp(3)

estimated

value

Hp(3)

u(Hp3)